Telemetering transmitter



March 9, 1948. R A, COLE Er AL 2,437,242

TELEMETERING TRANSMITTER March 9, 1948.

R. A. coLE ET AL TELEMETERING TRANSMITTER Filed April 29, l946` 3 Sheets-Sheet 2 March 9, 1948.

R. A. COLE El' AL TELEMETERING TRANSMITTER Filed April 29, 1946 3 Sheets-Sheet 3 mnimlilll LME@ /ff Patented Mar. 9, 1948 2,437,242 TELEMETERNG TRANSMITTER Robert A. Cole, Moline, Ill., and Donald I. Smith,

Vin

cent, Ohio Application April 29, 1946, Serial No. 665,719 6 Claims. (Cl. 177-380) (Granted under the act of March amended April 30, 1928; 370 0.

The invention described herein may be manufactured and used hy or for the Goverment for governmental purposes without the payment to us of any royalty thereon.

This invention relates to e. telemetering appa= ratus and method which .is adapted to transmit by radio, the indications and 4behavior of s. mul.- tlplicity of instruments, for example, those used on test aircraft. It may also be used to transmit indications ci the positions of airfoil surfaces, or

Whether servo motors are on or Moll.

One ci the objects ci the invention is to pro vide a system of this class which will produce e, graphic record of the behavior of a condition or motion to lee telemetered directly and compara= tively with other conditions simultaneously telemetered so that the graphs may be compared for any given instant or interval of time.

Another object is to provide an apparatus which uses no ink for recording. Inks are objectionable because ci exhaustion, freezing, premature drying and many other reasons.

A further object is to provide a method of sie nal generation in which momentary intertopIl tions of a carrier wave will he sent out in a series and the position of the interruptions to eachother will be proportional to the motion or condition being telemetered. Suchmomentary interruption does not interfere with the synchronization signal because of its short duration. @ther objects, such as the provision of e. simple, compact appa ratus for accomplishing the alcove .results will ce evident from the context.

in the drawings,

Fig. l is a schematic view of the signal generating and transmitting equipment.

Fig. 2 is a. schematic View ci the receiving, amra plifying and record-generating equipment.

Fig. 3 is a plan view of the actual signal goof erator and transmitter.

Fig. i is an exploded view of tor.

Fig. 5 is a circuit diagram of the sional genera tor and transmitter.

Fig. 6 is a side elevation of the actual receiver and recorder.

Fig. 7 is a plan view of the actual recorder.

TRANSMITTER Schematic presentation In Fig. l, a direct current motor Hl drives a shaft Il upon which is mounted a drum l2 for concentric rotation. The drum is made of insulating material such as synthetic resin plastic or vulcanized fiber. A helix I3 of conductive matethe signal genera rial preferably fiat copper wire, is inlaid into the drum so as to be wrapped about the cylinder thru 360 and is grounded to shalt H. Mounted about the periphery ol cylinder i2 at preferably, but not necessarily, the middle point of its length, there are a multiplicity of linearly movable con" tacts i4. Such contacts may have any suitable shape, but preferably they are made with a cym iindrical portion l5 and a stylus portion l5. A coil spring il, made preferably ol' beryllium cop per, is connected co=axially with one end of cylinder l5 and the outer end of such spring alcuts a solid immovable sindaco. Suitable connection is made to the other end oi' cylinder l5 to con-1 nect the motion to he telemetered with the latter. Spring il will then return cylinder l5 to the zero point after cessation of the telemetering motion which has displaced it either to the left or to the right of that point. All contacts lll-I t do not necessarily have the same nero point. An enveloping cylinder i3 having a number oi longtudinai bores i9 for accommodating the movement of stylus l5 is used to house contact cylinders l5 and guide them in a straight line es the telemetering forces move it hack and forth over the registering cylinder l2. .All contacts i4 are connected electrically to separate leads 23 through transverse openings in the Wall of cyl-- inder i3.

At the free end ci shaft ll there is a tone senerator 20, the pitch oi which is proportional to the speed of motor id. The tone, er audio fre fluency, is used to modulate a conventional radio transmitter 22 hy ineens o a modulator 2 l. Any suitable place on the transmitter is tapped by a lead 23 to carry the modulated carrier wave to all contacts l, altho there is no now of such current thru the contacts i4 until they ect to ground the carrier current thru helix i3 thence to shaft H which is provided with a ground 24. Normally the carrier current is delivered to antenne 23e thru lead 23h, 'this using one branch of output lead 23 from the transmitter. The other branch, 23a, connects with lead i9 which in turn connects all contacts I4.

It will be evident, therefore, that the transmitting system operates as follows: Motor lll rotates shaft ll, cylinder l2 which is in effect a rotary switch and tone generator 20 at an identical high speed, which can he judged by the pitch of the tone. The sti/ll I6 make contact serially with helix wire i3 at intervals which are determined by the longitudinal position of contacts I4 on cylinder l2. Such positions are in turn dependent upon the telemetering forces or motions impressed upon cylinders i5 of contacts I4 and ACTUAL CONSTRUCTION or SIGNAL GENERA'ros Referring now to Figs. 3, 4 and.5, it will be seen that the actual construction of the signal generator has been changed from that described in the schematic presentation so as to make the apparatus compact and rugged. Fig. 4 shows the few parts that are necessary to make up the mechanical assembly. Fig. 4 shows a simpliilcation of the circuit brought about by the elimination of the tone generator and the addition of a high frequency oscillating tube and associated circuits.

In this construction. shaft carries upon its outer end a worm wheel which is driven by a worm |0| which is in turn driven by motor l0. Drum I2 fit enveloping cylinder I8, its shaft being supported in ber or synthetic resin bearings |02 The other end of the shaft is supported in ball bearings |03` supported in insulating block |04 which is attached to the end of cylinder i8. A spur gear |05 is mounted on shaft I and is supported in insulating block |06, It abuts a second spur gear |01 which is xedly supported on an insulating block. The latter and block |04 are drilled with as many small holes |09 as there are bores |8a in cylinder I8. The holes and bores register. Their purpose is the accommodation of fine but strong wires which connect the contacts |5 with the forces or positions to be telemetered. Conductors 23 connect the inner contacts I5 with the transmitter 22.

The gears |05 and |01 are in capacitative electrical relation. therefore, when gear |05, which is insulated from gear |01 revolves, the effect is that of a variable condenser. The capacity changes according to whether the teeth are opposite each other or opposite a trough. The change is superposed upon the basic capacity which resides inherently in the gears when they are considered as shaped masses of metal facing each other at a fixed distance and under fixed electrical conditions.

Referring now to Fig. 5, the circuit represents an oscillator employing a high frequency miniature oscillating tube |20 (type 6C4 preferred) in a tank circuit. |2| is the tank coil and its tank condenser is |22. Therefore the circuit is that of a self-excited oscillator feeding energy back to the tube grid through a condenser |23. Resistances |24 and |25 provide grid bias through grid current flow. The cathode of the tube is grounded. The filament is heated by a storage battery |26 or equivalent supply. An antenna |21 is attached to the tank coil |2| through a condenser |28 which insulates the antenna from the high voltage D. C. Contact |29 goes to the center top of the tank coil which is conventional in oscillator circuits. |30 is a fixed miniature mica condenser. A resistance |3| to ground is provided to earth any D, C. which might leak thru condenser |30. created by the proximity of collar 0r blOck l |32 is a fixed capacitance and gear |05. Capacitances |33 and |355 are created by gears and |il`| being in proximity, |33 being the fixed or basic capacitance and |34 the variable one caused by the rotation of the gears. Signals received by the helix i3 or |2| are collected to short out part of the grid bias resistor |25. Therefore these signals amplitude modulate the oscillator as well as frequency modulate it. However, the frequency modulation is the only part used. The carrier frequency amounts to about sixteen megacycles.

Rncarvna am Resonans Schematic presentation A conventional receiver 30 is divided as to its output. A portion is carried to a filter 3| which permits passage of the audio component of the carrier wave, i. e., the synchronization frequency. This output is amplied by an amplifier 32 and the amplifier output fed to a special motor 33. The latter is substantially an inverter (Bendix type No. 12117-2-B), but may alternatively be a synchronous motor. If an inverter is used (which is preferred). it is driven by its D, C. portion. A resistor 86 is provided in the D. C. supply to cause poor D. C. speed regulation. The amplified modulated carrier wave above referred to, is fed into the A. C. portion of the inverter and serves to hold it in proportional synchronism to the transmitting cylinder I2 and in exact synchronism with the mechanical transmitter, i. e., the tone generator.

Attached to the other output branch of receiver 30 is another lter 35 which permits the passage of impulses, but not of the synchronization frequency. An amplifier is also provided for this filtered signal and the output may be fed directly to a recorder 38 or preliminarily to a timing signal generator 31.

The recorder is essentially a thin metal band 38 of a length corresponding to or proportional to the diameter of cylinder |2. It passes over driver pulley 46 and drlven pulley 41 and is provided on its periphery with equi-spaced contacts 33 or number equal to the number of contacts I4 of the transmitter. It is mounted on the drive shaft 40 of inverter 33, A spring-pressed contact 4| closes the circuit at the extreme end of shaft 40 beyond the point at which the recorder disc 38 is mounted.

Beneath the band 38, there is a continuous strip 44 of the sensitive paper known as Teledeltos. It is a paper which becomes marked at that point at which an electric current passes thru it. The strip may be bent arcuately to touch the disc at the periphery contacts 39, thereby giving the stripa troughed shape. In this position the marks 45 made upon it are easy to read. Means, 43, for example, toothed wheels cooperating with slots in the paper margins may be used to move the paper continuously are provided.

Operation of the receiver-recorder is as follows: D. C. from mains is applied to the D, C. side of inverter 33. This force does most of the driving. The poor speed regulation caused by the resistor 34 renders the D. C. motor susceptible to speed control by its A. C. side. That side tends to run in synchronism with the filtered audio component supplied to it by filter 3| and amplier 32. Therefore motor 33 is a speed-governed synchronous motor of high torque.

The impulse filtering circuit energizes disc 38 electrically whenever the circuit is broken by the transmitting cylinder I2. thereby causing a current to flow from contact ll thru band 38 and some one of contacts 39 thru the paper to a ground 42 under the paper thereby generating a graph line for each contact I4 of the transmitter. Since the order in which the telemetered conditions are fed to the transmitting cylinder I2 is known, it is evident that such order will be preserved, although none of the conditions is entitled to `be called the start or the finish of the series. If the identity of one of the conditions is recognizable from the kind of graph obtained, then all simultaneous graph lines will be identifiable from their positions in relation to the iirst. If no graph is suiciently characteristic to identify a telemetered condition from it, the position of one of the graphs in the series can be determined by disconnecting all contacts i4 except one, telemetering that one locating its graph and then re-connecting the rest of the contacts I4.

In order to measure the passage of time on the graph, the presence in the circuit of timer `3'! is necessary. By sending out a signal of some duration at spaced intervals, a line can be drawn on the paper which is indicative of elapsed time and is readily distinguishable from other impulse marks.

By a slight modication of the transmitting circuit, the necessity for grounding the shaft il or the helix i3 can be avoided. In such modification, the contacts it are connected into the grid circuit of the transmitter to bias the grids negatively upon either making or breaking contact with helix i3. An action is thus achieved which has the effect of momentarily blocking the output of the set instead of diverting that output to ground. Any competent electronic engineer in possession or this disclosure can make this modi iication, It is indicated in Fig. l by the dotted line in the antenna circuit, which line doe-s not carry current When the transmitter is being oper ated to be intermittently grounded to generate signal. When signal is to be blocked, not grounded, the dotted line would carry full output, but lead 23h would be eliminated.

Essonnes- ACTUAL CoNsTRUcrioN The construction below described lends itself especially Well, on account or" its compactness, to installation aboard a mother aircraft, i. e. one which accompanies the iilght of a test model.

A base l5@ -is provided with form uprights each pair of which support a right angled slotted frame it?. A crosspin its in each frame :forms the axle of each pulley it and il respectively. The inverter 3S is arranged to drive pulley 47 by means of a worm lili and worm wheel 55, the latter being mounted on axle i553. Between the frames i552 is a threaded spacing bar i557 having an in 'ternaliy threaded collar 58. By this means the length of the bar can be adjusted to regulate the tightness ol band 38 over pulleys #i6-4l.

Supporting a roll of current sensitive paper 44, there is a box-like sheet metal structure 59 behind the left frame l52. Paper for this roll passes under pulley lll and band 38 and thru a sheet metal housing itil. The latter supports a flattening idler roll ll. A synchronous motor i62 is arranged to drive the paper thru slots i63 in its margin by means of sprockets 53.

The invention claimed is:

l. In a telemetering system, a radio transmitter, a monotone generator, means for modulating the carrier Wave transmitted by the transmitter by the tone generator, a rotary switch of the drum type adapted to key the output wave generated by said transmitter said switch comprising a non-conducting cylinder, a conductive helix disposed on the cylindrical surface thereof, a surrounding non-conducting cylinder for said drum having a plurality of circumferentially incomplete passages longitudinally disposed therethrough, slidable contacts arranged in said passages and in contact with the outer cylindrical surface of said drum, means for individually varying the position of said contacts longitudinally along the surface of the drum in accordance with conditions to be telemetered, a motor arranged to drive said rotary switch, a shaft i'or said motor, said switch and said generator being mounted thereon to rotate at the same speed.

2. A system according to claim 1 in which the rotary switch is arranged to ground the audio component of transmitter output for an extremely short time at instants determined by the posi tion of the contacts in regard to a dimension of said switch.

3. In a telemetering apparatus, a radio transmittel, tone generating means connected and adapted to modulate the output of said transmittern rotary means comprising a non-conducting cylinder, a conductive helix disposed on said cylinder, a plurality of contacts movable longitudinally in response to conditions to be telemeter disposed about said cylinder and capable of making and breaking contact with said helix, a shalt driving both the cylinder and the tone generating means, a transmitter output circuit in which said movable contacts are included, said means togather constituting an apparatus capable of transmitting a tone modulated carrier wave divided by short time intervals during which no audio component of the carrier Wave is transn mitted, salti intervals being spaced proportionally to the setting or" conte ;l with respect to the longitudinal dimension ci' said cylinder.

d. ln a telemetering device, a transmitter com- Mrising a cylindrical drum of nonfconducting material, a central shaft therefor, an inlaid helix of conductive Wire in the surface of said drum, a housing for said drum which comprises a hollow cylinder of non-conductive material, the walls of said cylinder having a multiplicity of longitudinally bored cylindrical passages, slidable contacts within said passages, means for attaching each of said contacts to force to be telemetered, a motor for rotating said drum, a high frequency seit excited tank circuit arranged thru the inlaid wire on said drum and adapted to be interrupted for extremely short periods of time by said slidable contacts, said circuit including a high fre cuency oscillator tube, a tank coil and a tone generator,7 said generator comprising two substantially abutting spur gears insulated from each other, one being so mounted as to be stationary and the other revolubly mounted on 'the drum shaft, the gears being electrically so connected as to act as a variable condenser.

5. A system according to claim l in which the variable-position contacts are connected into the grid circuit of the radio transmitter to bias the grids thereof negatively upon the variable-position contacts either making or breaking contact with the rotary switch.

6. In a telemetering system; a transmitter comprising a radio transmitter capable of transmitting a carrier wave, means for modulating the carrier wave and means for interrupting said modulated carrier wave in response to a condition outside said transmitter which condition is to be telemetered, said means comprising a drum of non-conducting material, a. conductive helix inlaid in said drum, a. surrounding non-conductive cylinder for said drum having a. plurality of circumferentially incomplete passages longitudinally disposed therethrough. an insulating wall for one end of said drum. a drive shaft extending through said drum and said wall, coil springs anchored to said wall, slidable contacts attached to said coil springs and arranged in said passages, said contacts being' disposed to contact said drum and mechanical wire connections between said contacts and instruments indicating the conditions to be telemetered.

ROBERT A. COLE.

DONALD I. SMITH.

file of this patent:

UNITED STATES PATENTS Number 

